For Postmortem Identification of Incinerated Remains, Amalgam Is More Resistant to Morphological Change when Compared to Resin Composites

Clinical Question

In a postmortem incinerated human dentition, will amalgam or composite better resist morphological changes associated with heat so that antemortem dental records can be used for victim identification?

Clinical Bottom Line

In incinerated victims, while both amalgam and composite are reasonably reliable for victim identification using antemortem records, amalgam is more likely to resist morphological changes when exposed to incineration temperatures. Therefore, if a victim has dentition with a mix of amalgam and composite restorations, beginning the identification process by comparing a postmortem radiograph of the amalgam-restored tooth to antemortem records or radiographs may be the more efficient, accurate and preferred approach.

Three groups of teeth - unrestored (n = 30), endodontically treated and Class I amalgam restoration (n= 30), and endodontically treated and Class I composite restoration (n= 30) - were exposed to an experimental range of high temperatures. Composite restorations maintained their morphology until about 600C. At 800C the composites were in place but seemed to undergo state change. At 1100C, the composite restorations were noted as being in a “remarkably altered state.” Amalgam restorations began to see fissures between the tooth tissue and the filling at around 800C. However there were no changes in shape with the amalgam restorations until 1100C.

Four groups of teeth with no restoration (n = 10) or amalgam (n= 10), glass ionomer (n= 10), or composite resin (n = 10) restorations were exposed to incineration temperatures. Amalgam restorations were significantly more resistant to morphological change under high temperatures. Amalgam showed surface bubbles at 200C, lost their marginal seal at 400C, but remained intact until about 1000C. In comparison, composite restorations began to lose marginal seals around 200C, displayed volumetric contraction towards the floor of cavity at 400C, and transitioned to an altered morphological state around 600C. The article states that at 1000C, the composite restorations were dislodged, which contradicts other studies that show that composite remained in place but was severely altered.

Evidence Search

"Forensic Dentistry"[Mesh] AND "Dental Restoration, Permanent"[Mesh]

Comments on
The Evidence

Validity: Both of these articles were in vitro lab studies done with various dental restoration materials. Since the restorations were prepped and filled to strict criteria, the researchers could not be blinded in either study. Another limitation of these studies is that the samples lacked the true soft tissue protection from incineration, and the samples had a more direct source of heat than would occur in the presence of cheek and lip protection. An additional concern is the length of time that the samples were exposed to the elevated temperatures; the first study ramped up to the target temperature and removed the samples immediately while the second study exposed the samples for 15 minutes of thermal shock. These simulations may not accurately describe incineration situations where the body is exposed to prolonged elevated temperatures.
Perspective: Although amalgam is more resistant to morphological change at high temperatures when compared to composite., both can be used for accurate postmortem identification. If the entire restoration has been separated from the crown, there are additional methods to infer the former presence of a particular restorative material such as the appearance of retentive form or the presence of their combusted byproducts on the cavosurface fragments. Additional studies on the predictability of what restoration was formerly present but separated by heat disturbance should be explored.

Applicability

The study results apply to a very specific population of unidentified postmortem individuals who had been exposed to temperatures greater than 200C. This data is very useful for the forensic odontologist because the predictable incineration patterns of various dental restorations can help determine cause of death by indicating what temperature the tissue was exposed to. When exposed to high temperatures, these studies prove that the postmortem incinerated samples will predictably retain enough of their original characteristics to reliably identify the victim given accurate antemortem records. It has been established that victims with amalgam or composite restorations may be accurately identified when comparing postmortem radiographs to antemortem radiographs. However, amalgam proves to be more resistant to morphological change up to temperatures of 1000C while composite tends to alter its state near the 600C mark. Therefore, if the victim was exposed to temperatures greater than 600C, a heavier weight may be placed on the morphologic accuracy of the postmortem amalgam restorations over the composite restorations.

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